The spec forbids persistent bottom sheets from overlapping the app bar. There
are also some fancy scroll-linked effects that we're supposed to do with
persistent bottom sheets, but those will need to wait for another patch.

Fixes #5143

This requires all AnimationController objects to be given a
TickerProvider, a class that can create the Ticker.

It also provides some nice mixins for people who want to have their
State provide a TickerProvider. And a schedulerTickerProvider for those
cases where you just want to see your battery burn.

Also, we now enforce destruction order for elements.

* Added OverscrollIndicatorEdge et al

* RefreshIndicator only clamps its scrollable edge

* added a test

* Updated the test

* fixed lint-os

* fixed a typo

* Scrollable should restore its viewport dimensions when it reappears

* removed an accidental commit

* updated per review feedback

This eliminates all the issues around the horizontal page transition. I also improved the back gesture animation, and added fling support.

BUG=https://github.com/flutter/flutter/issues/5678
BUG=https://github.com/flutter/flutter/issues/5622

The iOS transition is the more buggy part of this feature, and it wasn't
disabled. Let's just leave them enabled while I work on improvements.

Also added a regression test for the back gesture on iOS and android.

Doesn't do any of the fancy effects. Just lets the user control the
back transition by sliding from the left, like a drawer. Hero
transitions are disabled during the gesture.

BUG=https://github.com/flutter/flutter/issues/4817

Fixes https://github.com/flutter/flutter/issues/5131

If the scaffold is new and has a floating action button, we skip the entrance
animation for the fab.

Fixes #4445

Anywhere that accepted IconData now accepts either an Icon or an
ImageIcon.

Places that used to take an IconData in an `icon` argument, notably
IconButton and DrawerItem, now take a Widget in that slot. You can wrap
the value that used to be passed in in an Icon constructor to get the
same result.

Icon itself now takes the icon as a positional argument, for brevity.

ThemeData now has an iconTheme as well as a primaryIconTheme, the same
way it has had a textTheme and primaryTextTheme for a while.

IconTheme.of() always returns a value now (though that value itself may
have nulls in it). It defaults to the ThemeData.iconTheme.

IconThemeData.fallback() is a new method that returns an icon theme data
structure with all fields filled in.

IconTheme.merge() is a new constructor that takes a context and creates
a widget that mixes in the new values with the inherited values.

Most places that introduced an IconTheme widget now use IconTheme.merge.

IconThemeData.merge and IconThemeData.copyWith act in a way analogous to
the similarly-named members of TextStyle.

ImageIcon is introduced. It acts like Icon but takes an ImageProvider
instead of an IconData.

Also: Fix the analyzer to actually check the stocks app.

This patch starts working through the missing dartdocs in widgets.dart.

Previously the floating action button would disappear during transitions. Now
we animate properly. I've also centralized the animation in Scaffold instead of
spreading it across the Scaffold and the FloatingActionButton.

Fixes #1718

Making progress towards document all public APIs in material.dart. We're still
missing a few odds and ends (as well as missing docs in tabs.dart,
tooltip.dart, and two_level_list.dart).

This patch addresses late-breaking comments on previous patches.

This patch adds an option to Scaffold to disable resizing the body to avoid the
window padding. This lets developers create layouts that are stable when the
keyboard overlays the app.

Fixes #3565

* Gallery Smoke Test

* Make IconButtons as big as possible

* Remove Scaffold scrollable_key demo usage

Also, clean up a few interfaces that looked awkward when writing docs.

Fixes #463

Adds some names for common FractionalOffset values.

Now MediaQuery.of always returns a non-null value. By default, you get the
values associated with the current ui.Window.

Fixes #2894

* left -> leading (Removes an LTR bias)
* center -> title (Widget was actually centered)
* right -> actions (Removes an LTR bias, asymmetric with leading)

Fixes #2348

This patch renames StatelessComponent to StatelessWidget and
StatefulComponent to StatefulWidget.

Fixes #2308

Fixes #1382

Fixes #459